Re: [Qemu-devel] coroutines and block I/O considerations

[Anthony Liguori <anthony@codemonkey.ws>]

On 07/19/2011 05:10 AM, Kevin Wolf wrote:
> Am 19.07.2011 10:06, schrieb Frediano Ziglio:
> They are still all running in the same thread.
>
>> 2- memory considerations on coroutines. Beside coroutines allow more
>> readable code I wonder if somebody considered memory. For every
>> coroutines a different stack has to be allocated. For instance
>> ucontext and win32 implementation use 4mb. Assuming 128 concurrent AIO
>> this require about 512mb of ram (mostly only committed but not used
>> and coroutines are reused).
>
> 128 concurrent requests is a lot. And even then, it's only virtual
> memory. I doubt that we're actually using much more than we do in the
> old code with the AIOCBs (which will disappear and become local
> variables when we complete the conversion).

A 4mb stack is probably overkill anyway.  It's easiest to just start 
with a large stack and then once all of the functionality is worked out, 
optimize to a smaller stack.

The same problem exists with using threads FWIW since the default thread 
stack is usually quite large.

Regards,

Anthony Liguori